Center Of Pressure Sway Area Research Articles

Wobble Board Performance: A Practical and Useful Quantification in Balance Assessment

Balance is integral in ankle injury prevention and therapy, especially in high-risk sports like volleyball. For balance assessment, the recommended wobble board (WB) performance (i.e., time at equilibrium) has never been compared with the gold standard. The objective was to investigate the relationships of force-plate-derived center of pressure (CoP) with WB performance and the accuracy of WB-derived CoP estimates. Twelve high-level volleyball players completed six unipedal standing trials on a computerized WB. WB tilt angles and CoP were obtained simultaneously via tri-axis accelerometers on the WB (200 Hz) and a force plate (1000 Hz), respectively. WB performance, polynomial-transformed CoP estimates, and CoP fractal sway, sway area, and mean sway velocity were assessed via Pearson and concordance correlation, root mean square errors, and dependent t-tests. WB performance was related with CoP sway and sway area (|rlinear| = 0.714–0.842, |rnonlinear| = 0.833–0.910, p < 0.01). The strongest concordance (0.878–0.893, p < 0.001) and smallest errors (6.5–10.7%) were reported for anterior–posterior sway and sway area. Moderate to excellent relationships between the WB performance and force plate CoP variables supported the usefulness of WB performance and estimates (especially sway area) in balance assessment. Furthermore, this study presents recommendations for future analyses and modeling approaches to reflect the complexity of postural control.

Modern smartphone usage can negatively impact postural balance while standing on dynamically challenging grounds

BackgroundWhile several studies have explored the impacts of smartphone usage on postural balance, their tasks are limited to texting or calling, and the studies were performed on rigid ground. Research questions1.How does modern smartphone usage, specifically taking selfies or posting statuses on social media, affect balance?2.How does their interaction with challenging ground conditions affect balance? MethodsSixteen healthy young adults were recruited to perform two smartphone tasks: taking selfies and posting statuses on social media; participants were standing on four different grounds: rigid, foam-based compliant, robot-simulated compliant, and robot-simulated oscillatory grounds. The center-of-pressure (CoP) under each foot was recorded via force plates and the net CoP was calculated. Temporal, spatial, and control aspects of postural balance were analyzed by virtual time-to-contact (VTC), CoP path length (PL) and sway area (SA), and switching rate (SR), respectively. Two-way repeated measures analysis of variance (ANOVA) tests were performed for each dependent variable to compare the mean differences between smartphone tasks and ground conditions and their interaction effect. Paired t-tests with Bonferroni correction were used to determine significant differences in post-hoc analyses. ResultsVTC decreased significantly whereas CoP PL and SA increased significantly during smartphone usage (all p-values <0.001). Interaction effects between task and ground condition (all p-values <0.001) were observed in all measures but SR, implying that the effect of smartphone usage on postural balance can significantly change depending on the ground condition. SignificanceThese results highlight the potential fall risks due to the impact of modern smartphone usage on standing balance. Understanding the effect of smartphone usage on standing balance and the interaction effect with various ground conditions opens the door for potential balance assistive devices and mobile phone applications to minimize falls.

Influence of age on static postural control in adults with type 2 diabetes mellitus: a cross-sectional study.

It was the aim of this study to assess static postural control characteristics in people with type 2 diabetes mellitus (T2D) of different ages using a force platform. A relationship was also established between static postural control parameters and age in this study. A total of 706 participants with T2D were included in this study. The participants were stratified into three age groups: Group 1 (<60 years old), Group 2 (60-70 years old), and Group 3 (>70 years old). Static postural control assessment during two-leg stance was performed on a force platform by all participants. The center of pressure (CoP)-related parameters were measured under two stance conditions (eyes open and closed). Kruskal-Wallis tests were applied to explore the difference among the different age groups. Multivariate regression analysis was performed to determine the relation between age and static postural control parameters. Group 1 (<60 years old) had significantly less CoP total tracking length (TTL), sway area (SA), and CoP velocity along the Y direction (V-Y) under both eyes-open and eyes-closed conditions compared with Group 2 (60-70 years old) and Group 3 (>70 years old). Group 1 (<60 years old) had significantly less CoP maximum sway length along the X direction (MSL_X) and longer tracking length each area unit (TTL/SA) under the eyes-open condition compared with Group 2 (60-70 years old) and Group 3 (>70 years old). There was a significantly positive correlation between age and the most static postural parameters such as CoP TTL, SA, MSL-X, MSL-Y, and V-Y. There was a significantly negative correlation between age and TTL/SA. This study suggested that older T2D participants had worse static postural control ability than younger ones. Most static postural parameters presented a significant correlation with age; the higher the age, the worse the static postural control.

Investigation of Static Balance Differences between Adolescents with Idiopathic Scoliosis and Healthy Age-matched Adolescents: A Cross-sectional Study

Background: The aim of this study was to compare postural control between Adolescents with Idiopathic Scoliosis (AIS) and healthy adolescents. Methods: In this cross-sectional study, 20 AIS adolescents with a right thoracic curvature between 10 and 45 degrees and 20 healthy adolescents were matched to compare postural control. Postural control assessments included Center of Pressure (COP) range and COP velocity in the Anteroposterior (AP) and Mediolateral (ML) directions, and the COP sway area in the standing position with opened eyes and closed eyes by the force plate. Results: This study showed that the postural control variables in AIS adolescents and healthy adolescents in terms of COP range, COP velocity, and COP sway area in standing positions with open and closed eyes were significantly different with those of AIS adolescents being worse than those of healthy adolescents (all p&lt;0.001). The interaction between Group and Condition (eyes open and eyes closed) was not significant for all variables (all p&gt;0.05). Conclusion: Differences in the postural control measures indicate postural instability in adolescents with AIS compared to healthy adolescents.

Functional balance training in people with Parkinson's disease: a protocol of balanceHOME randomized control trial with crossover.

Balance disturbances in Parkinson's Disease (PD) are usually assessed in a single-task as well as standard balance physiotherapy is carried out in isolated environments. Conversely, daily activities are developed in highly challenging environments. Although functional balance training (FBT) is included in the latest protocols, several methodological issues have not yet been considered. In the proposed single-blinded randomized control trial with crossover (NCT04963894), the aims are (1) to quantify the effects achieved by domiciliary FBT (balanceHOME program) in participants with and without cognitive impairment, and (2) to compare them with the effects of a passive-control period and a conventional face-to-face physiotherapy program for PD. The initial recruitment was estimated at 112 people with idiopathic PD. Two-thirds of the participants will be randomized to one of the two groups to make the crossover. In contrast, the other third will do a face-to-face group program only. The balanceHOME protocol consists of challenging balance exercises incorporated into functional daily tasks, developed in-home and conducted two times per week for 60-min over an 8-weeks period. The primary strategy will consist of splitting functional tasks of daily life into static and dynamic balance components, besides standardized facilitate and disturbing strategies to execution of each exercise. Biomechanics and clinical performance of balance and gait, perception of quality of life, cognitive and mental functioning, and severity of PD will be measured at baseline (T0), post-8 weeks training (T1), and follow-up (T2). The primary outcome of the study will be the center of pressure sway area. The secondary outcomes consist of biomechanics and clinical variables related to static and dynamic balance. Outcomes from biomechanical of gait, quality of life, cognitive and mental state, and severity of PD, represent the tertiary outcomes. The balanceHOME program standardizes the FBT in demanding and daily environments for people with PD who prefer individualized treatment from home. This is the first time that the effects of group versus individual balance rehabilitation have been compared in people with and without cognitive impairment and evaluated in complex environments. This still-to-be-finished study will open the possibility of new strategies according to changes in post-pandemic therapeutic approaches.

View-Invariant Center-of-Pressure Metrics Estimation With Monocular RGB Camera

Center of pressure (CoP) metrics, including CoP path length and sway area, have been used as gold standard measurements of postural and balance control in biomechanical studies. A recent study of computer-vision-based CoP metrics estimation from 3D body landmark sequences offers a more portable and comprehensive solution than conventional force plate methods to obtain these important metrics for real-time evaluation of balance control. However, obtaining accurate 3D body landmarks requires a calibrated motion capture system or on-body markers, which involves lengthy data collection and processing time and limits their implementation in home and clinical environments. Existing methods that instead use 2D body landmarks fail to adapt to different camera positions. To overcome these challenges, we propose a view-invariant deep learning framework for video-level CoP metrics estimation, including CoP path length and sway area, using pose dimension lifting and graph convolutional network (GCN). This work is the first step toward obtaining gold-standard CoP metrics with an accessible, monocular RGB camera. We propose to use a dimension lifting convolutional neural network (CNN) to obtain view-invariant 3D body landmark features from 2D body landmarks. We also propose a two-stream regression model using GCN and discrete cosine transform (DCT) for a robust CoP metrics estimation. To facilitate the line of research, we release a novel multi-view body landmark dataset containing 2D body landmarks of a wide variety of action patterns from four different camera views with synchronized CoP labels and corresponding 3D body landmarks, which enables cross-view evaluation with different camera angles. We subsequently validate the proposed method through a cross-dataset training by training the dimension lifting model on an existing balance dataset and evaluating the CoP metrics estimation on the multi-view body landmark dataset. The experiments validate that our framework achieves state-of-the-art accuracy for both CoP path length and CoP sway area using a monocular RGB camera input for unseen views.

The effectiveness of Schroth exercises added to the brace on the postural control of adolescents with idiopathic scoliosis: Case series.

One of the disorders that may cause changes in body posture and impair postural control is adolescent idiopathic scoliosis (AIS). Scoliosis-specific exercises, such as the three-dimensional Schroth method added to the brace, may be able to help these patients improve their postural control. The aim of this study was evaluating the effect of Schroth physiotherapy scoliosis-specific exercises added to the brace on AIS patients' postural control. It is a case series study on twenty-three AIS patients. They were treated using the Schroth method and brace for three months, with the first five sessions lasting two weeks and subsequently one session per week. Postural control assessments include center of pressure (COP) range and COP velocity in the anteroposterior (AP) and mediolateral (ML) directions, and the COP sway area in the standing position with opened eyes and closed eyes by the force plate. The angle of trunk rotation (ATR) was assessed by the scoliometer. The methods are consistent with the PROCESS 2020 guidelines. The Schroth method and brace also significantly improved the variables of postural control variables in terms of COP range (p<0.001), COP velocity (p<0.001), and COP sway area in standing positions with opened and closed eyes (p<0.001, p<0.001) as well as ATR (p<0.001) in AIS patients. Schroth method and brace improved the postural control and trunk rotation of AIS patients.

Trunk balance, head posture and plantar pressure in adolescent idiopathic scoliosis.

The relationship of trunk balance with head posture and plantar pressure is unknown in patients with adolescent idiopathic scoliosis (AIS). To investigate the relationship of trunk balance with head posture and plantar pressure by analyzing the imaging data of patients with AIS. This retrospective study was performed on 80 AIS patients who had whole spine frontal and lateral radiographs, and the imaging parameters were measured and analyzed. The coronal trunk imbalance rate was 67.5%, the trunk offset direction was towards left in 65 cases and right in 15 cases, and the head offset direction was towards left in 66 cases and right in 14 cases. The sagittal trunk imbalance rate was 57.25%. The distance of apical vertebrae and head offset in the coronal trunk balance group was significantly (P < 0.05) smaller than that in the imbalance group. The apical vertebrae offset distance and head offset distance were positively correlated with the tilt angle of trunk (r = 0.484 and 0.642, respectively, P < 0.05). The difference in the percentage of pressure load on the left and right foot was significantly (P < 0.05) greater in the coronal imbalance group than that in the balance group.The center of pressure (COP) sway area was significantly (P < 0.05) larger in the overall trunk imbalance group (both coronal and sagittal imbalance) than in the balanced group. Most AIS patients have trunk imbalance which is severer on the coronal than on the sagittal plane. AIS patients with trunk imbalance show more significant local deformities, greater head offset, greater COP sway area, and decreased head and standing stability.

TEST–RETEST RELIABILITY OF POSTURAL SWAY MEASURES DURING STATIC STANDING BALANCE PERFORMANCE IN HEALTHY ELDERLY ADULTS

Little is known about the reliability of postural sway measures in healthy elderly adults. Moreover, there is no standardized balance test protocols such as an efficient number of repeated measurements for older people. Therefore, we investigated test-retest reliability of center of pressure (COP) variables during static balance performance in elderly adults. Twenty-five elderly adults (15 elderly men and 10 elderly women) were asked to perform quiet standing balance test on a self-developed force platform. COP-based variables, i.e., COP mean distance, sway area, mean velocity, mean frequency, maximum frequency, and maximum power amplitude were derived from the COP data. For the test-retest reliability of each COP-based variable, intraclass correlation coefficient (ICC) was assessed in two-trials and three-trials of balance test. Mean velocity showed the highest ICC values in all directions (ICC = 0.832–0.922). Frequency domain variables presented lower reliability than time domain variables. Additionally, elderly adults did not affect the number of repeated measurements in most postural balance variables. These results suggest that time domain variables are more reliable variables than frequency domain variable and that balance test of two trials might be rather effective for elderly adults. These findings can be used to develop an optimal protocol of static balance test and select postural balance variables for elderly adults.

Effects of Transcranial Direct Current Stimulation over the Primary Motor Cortex in Improving Postural Stability in Healthy Young Adults.

Simple SummaryTranscranial direct current stimulation (tDCS) is used as an adjuvant rehabilitation treatment to improve postural control and lower limb function. This study explored the effects of sham and anodal tDCS over the leg region of M1 on static and dynamic postural stability in healthy young adults. Jump-landing tasks were used to examine dynamic postural stability. Static postural stability was assessed by a single-leg stand on force plates with open eyes. Anodal tDCS had an immediate improving effect on static and dynamic postural stability, and might evolve as an adjuvant rehabilitation treatment to enhance postural deficits in the future.Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) is of increasing interest to improve motor performance in healthy adults and patients with respective deficits. This study aimed to examine whether tDCS over M1 can improve static and dynamic postural stability in young healthy adults. Seventeen healthy participants (mean age = 25.14 ± 2.50 (standard deviation, SD) years) received sham and anodal tDCS (2 mA) over the vertex at the Cz electrode position for 15 min. Static and dynamic postural stability were evaluated before and immediately after tDCS. The center of pressure (COP) sway area (COPSA) and COP maximum displacements to medio-lateral (COPML) and antero-posterior directions (COPAP) were used to evaluate static postural stability. The anterior–posterior stability index (APSI), medial–lateral stability index (MLSI), vertical stability index (VSI), dynamic postural stability index (DPSI), and time to stabilization (TTS) in forward (FL), 45° anterior lateral (LL), and 45° anterior medial (ML) direction landing, as well as the Y-balance composite score (YBTCS) were used to assess dynamic postural stability. The results showed that the LL-TTS (p = 0.044), non-dominant leg COPSA (p = 0.015), and YBTCS (p < 0.0001) were significantly improved in the real stimulation as compared with the sham stimulation session, and anodal tDCS significantly changed dominant leg COPAP (p = 0.021), FL-APSI (p < 0.0001), FL-TTS (p = 0.008), ML-TTS (p = 0.002), non-dominant leg YBTCS (p < 0.0001), and dominant leg YBTCS (p = 0.014). There were no significant differences in all obtained balance values in the sham stimulation session, except for non-dominant leg YBTCS (p = 0.049). We conclude that anodal tDCS over M1 has an immediate improving effect on static postural stability and dynamic performance in young healthy adults. This makes tDCS a promising adjuvant rehabilitation treatment to enhance postural stability deficits in the future.

Combined effect of gender differences and fatiguing task on postural balance, functional mobility and fall risk in adults with multiple sclerosis: A preliminary study

ABSTRACT Aim To investigate the gender difference effect on postural balance, functional mobility, and fall risk after performing a fatiguing task in adults with multiple sclerosis (MS). Methods Eleven women (30.91 ± 8.19 years) and seven men (30.29 ± 7.99 years) with relapsing-remitting MS performed a fatiguing task: three sets of the Five-repetition Sit-To-Stand Test (5-STST) were performed before and after the six-minute WalkTest (6MWT). Bipedal postural balance in eyes open and eyes closed conditions were assessed prefatigue (T0) and postfatigue (T3) using a force platform. Unipedal balance, functional mobility (Timed Up and Go Test), fall risk (Four Square Step Test) and fatigue [Visual Analogue Scale of Fatigue (VASF)] were assessed at T0 and T3. Heart rate (HR) and Rating of Perceived Exertion (RPE) were recorded before (only for HR), during and after the fatiguing task. Results Compared to women, men showed an impairment of posturographic parameters [mean center of pressure (CoP) velocity (CoPVm) in both conditions (p < 0.05); CoP sway area (CoPAr) in both conditions (p < 0.01)], unipedal balance on the dominant leg (p <0.001), mobility (p<0.001) and an increased fall risk (p < 0.05). No gender differences were observed in 6MWT, 5-STST, HR, RPE, and VASF. Conclusion This preliminary study showed that fatiguing task negatively affected postural control, mobility and fall risk only in men. These gender differences were inconclusive but could be taken into account in postural balance rehabilitation programs for MS persons.

Young Individuals Are More Stable and Stand More Upright When Using Rollator Assistance During Standing up and Sitting Down.

Four-wheeled walkers or rollators are often used to assist older individuals in maintaining an independent life by compensating for muscle weakness and reduced movement stability. However, limited biomechanical studies have been performed to understand how rollator support affects posture and stability, especially when standing up and sitting down. Therefore, this study examined how stability and posture change with varying levels of rollator support and on an unstable floor. The aim was to collect comprehensive baseline data during standing up and sitting down in young participants. In this study, 20 able-bodied, young participants stood up and sat down both 1) unassisted and assisted using a custom-made robot rollator simulator under 2) full support and 3) touch support. Unassisted and assisted performances were analyzed on normal and unstable floors using balance pads with a compliant surface under each foot. Using 3D motion capturing and two ground-embedded force plates, we compared assistive support and floor conditions for movement duration, the relative timing of seat-off, movement stability (center of pressure (COP) path length and sway area), and posture after standing up (lower body sagittal joint angles) using ANOVA analysis. The relative event of seat-off was earliest under full support compared to touch and unassisted conditions under normal but not under unstable floor conditions. The duration of standing up and sitting down did not differ between support conditions on normal or unstable floors. COP path length and sway area during both standing up and sitting down were lowest under full support regardless of both floor conditions. Hip and knee joints were least flexed under full support, with no differences between touch and unassisted in both floor conditions. Hence, full rollator support led to increased movement stability, while not slowing down the movement, during both standing up and sitting down. During standing up, the full support led to an earlier seat-off and a more upright standing posture when reaching a stable stance. These results indicate that rollator support when handles are correctly aligned does not lead to the detrimental movement alterations of increased forward-leaning. Future research aims to verify these findings in older persons with stability and muscle weakness deficiencies.

Effect of melatonin intake on postural balance, functional mobility and fall risk in persons with multiple sclerosis: a pilot study

Aim To assess the safety and the effect of a nocturnal melatonin (MEL) ingestion on postural balance, functional mobility and fall risk the following morning in adults with multiple sclerosis (MS). Methods Fourteen adults with relapsing-remitting MS (RR-MS) (28.36 ± 6.81 years) were evaluated before and after nocturnal ingestion of MEL (6 mg) or placebo (PLA). Evaluations included a posturographic test of static bipedal postural balance with dual-task in eyes open (EO) and eyes closed conditions, and a clinical test of unipedal balance. The physical performance tests were: Timed Up and Go test (TUGT) (mobility), Four Square Step Test (FSST) (fall risk), and Timed 25-foot walk test (T25FWT) (walking speed). Cognitive performance [Montreal Cognitive Assessment (MoCA) and Simple Reaction Time (SRT) tests] and sleep quality [Spiegel’s sleep questionnaire (SSQ)] were also assessed. Results In EO condition, MEL decreased the posturographic parameters [center of pressure (CoP) sway area (CoPAr), CoP path length (CoPL) and CoPL in the mediolateral axis (CoPLX)] more than PLA by 15.82% (p = 0.0006), 12.48% (p = 0.0004) and 14.25% (p = 0.0002), respectively. Durations of TUGT and FSST decreased following MEL session more than the PLA one by 14.52% (p = 0.017) and 19.85% (p = 0.0006), respectively. MEL increased the unipedal stance time, SSQ and MoCA scores more than PLA by 49.81% (p = 0.04), 32.21% (p = 0.004) and 11.87% (p = 0.008), respectively. Conclusion This pilot study showed that acute nocturnal MEL ingestion seems to be safe for enhancing postural balance, fun mobility and fall risk in RR-MS adults probably through improving sleep quality and cognitive function.

Relationship between static balance and gait parameters in preschool children

BackgroundPostural sway while standing reflects the degree of sensory integration function. The relationship between static balance and gait parameters in preschool children is essential for understanding which component of gait function is linked to the sensory integration function. Research questionWe aimed to clarify the relationship between static balance and gait in children, aged 2–6 years, with typical development MethodsA total of 105 children (48 girls, 57 boys) participated in this study. Static balance parameters were computed using positions at the center of pressure (COP) while standing (COP length, velocity, and sway area). Spatiotemporal parameters during gait were analyzed for stride length, step width, stance time, cadence, coefficient of variation (CV) of step length, and CV of stance time as gait variability. Pearson correlation coefficients were estimated to explore the relationship between age and static balance or gait parameters. Partial correlation analysis controlling for age was also performed to examine the relationship between static balance and gait parameters. ResultsA moderate association between age and static balance parameters and between age and gait parameters was found. Partial correlation analysis revealed that the variability parameters of gait were associated with the static balance parameters. No relationship was found between both spatial and temporal gait parameters and static balance parameters. SignificanceAmong the gait parameters that are considered to develop in early childhood, gait variability was associated with COP sway while standing, whereas stride length with increasing age was independent of any static balance parameters. Of the spatial, temporal, and variability parameters of gait, only gait variability maybe associated with the development of sensory integration function.

Postural Instability after Stepping on a Stair in Older Adults: A Pilot Study

This study aimed to examine how older adults (OA) control their postural stability after stepping on a stair in comparison to young adults (YA). Ten OA and 10 YA participated in this study. Participants ascended a single stair (15 cm high by 30 cm wide) which was secured atop one of the force plates. Ground reaction forces (GRFs) and center of pressure (COP) motion data were obtained from the force plate under the stair. After standing on the stair with both feet, GRFs and COP data for a 3 s duration were analyzed to assess postural variables, including time to stabilization (TTS), COP velocity (COPVEL), and COP sway area (COPSWAY). A significant difference in TTS in the anterior–posterior direction between OA and YA (p = 0.032) was observed, indicating that OA had difficulty stabilizing their body posture after the stair ascent compared to YA. For COP postural variables, no significant differences in COPVEL (p = 0.455) and COPSWAY (p = 0.176) were observed between OA and YA. Study findings indicate that older adults have less capacity to regain postural stability compared to young adults following a challenging dynamic movement.

Effect of local somatosensory stimulus on postural sway during sit-to-stand movement in the elderly

BackgroundSit-to-stand (STS) is a complex movement that requires successful postural control. Aging is a normal part of human life that leads to weakness of sensory capabilities, resulting in diminished postural control. Therefore, STS movement is a challenging task for the elderly. Local tendon vibration (LTV) can be utilized to assist STS of the elderly by improving postural control. Many studies have revealed that the LTV has various physiological positive effect. However, previous studies did not consider subjects’ individual difference for properties of applied LTV. Also, there are almost no studies to assist and to improve elder’s STS movement. Thus, the purpose of this study was to examine the influence of lower limb LTV on postural sway during STS in the elderly, and to examine whether a specific vibration frequency can increase postural control in the elderly.ResultsThe common characteristic differences between the elderly and younger population during STS movement were analyzed. In addition, the effect of vibration on the center of mass (COM) and the center of pressure (COP) variable responses in young adults and the elderly were investigated. As a result, the elderly exhibit larger COP sway area and higher COP mediolateral (ML) displacement than the young adults. In addition, the elderly generally have lower COM velocities in all directions compared to the young adults. It was found that COP and COM related to postural stability are affected when LTV of the 180 Hz, 190 Hz and 250 Hz is applied to the elderly. Particularly, the 190 Hz vibration induced significant reduction in COP sway area and COP ML displacement.ConclusionsThese results mean that the LTV contributes to stability of elders’ STS movement by reducing postural sway. Furthermore, a reduction of postural sway depends on frequency of the LTV. These findings suggest that individual response to characteristics of vibration must be considered, and imply that the LTV can be used as rehabilitation therapy to improve postural control in the elderly, and utilized in motion assistive devices to deliver apt vibration frequencies.Trial registrationCRIS, KCT0005434, Registered 25 September 2020, Retrospectively registered, https://cris.nih.go.kr/cris/index/index.do

The Disturbing Effect of Neuromuscular Fatigue on Postural Control Is Accentuated in the Premenstrual Phase in Female Athletes.

This study explored the fatigue effect on postural control (PC) across menstrual cycle phases (MCPs) in female athletes. Isometric maximal voluntary contraction (IMVC), the center of pressure sway area (CoParea), CoP length in the medio-lateral (CoPLX) and antero-posterior (CoPLY) directions, and Y-balance test (YBT) were assessed before and after a fatiguing exercise during the follicular phase (FP), mid-luteal phase (LP), and premenstrual phase (PMP). Baseline normalized reach distances (NRDs) for the YBT were lower (p = 0.00) in the PMP compared to others MCPs, but the IMVC, CoParea, CoPLX, and CoPLY remained unchanged. After exercise, the IMVC and the NRD decrease was higher at PMP compared to FP (p = 0.00) and LP (p = 0.00). The CoParea, CoPLX, and CoPLY increase was higher in the PMP compared to FP (p = 0.00) and LP (p = 0.00). It was concluded that there is an accentuated PC impairment after exercise observed at PMP.

Passive stretching decreases muscle efficiency in balance tasks.

The current study aimed to verify whether or not passive static stretching affects balance control capacity. Thirty-eight participants (19 women and 19 men) underwent a passive static stretching session, involving the knee extensor/flexor and dorsi/plantarflexor muscles, and a control session (no stretching, CTRL). Before (PRE), immediately after (POST), after 15 (POST15) and 30 min (POST30) from stretching (or rest in CTRL), balance control was evaluated under static and dynamic conditions, with open/closed eyes, and with/without somatosensory perturbation (foam under the feet). During tests, centre of pressure (CoP) sway area and perimeter and antero-posterior and medio-lateral sway mean speed were computed. Surface electromyography root mean square (sEMG RMS) was calculated from the vastus lateralis, biceps femoris, gastrocnemius medialis, and tibialis anterior muscles during MVC and during the balance tests. Hip flexion/extension and dorsi/plantarflexion range of motion (ROM), maximum voluntary contraction (MVC) and sEMG RMS during MVC were measured at the same time points. After stretching, ROM increased (≈6.5%; P<0.05), while MVC and sEMG RMS decreased (≈9% and ≈7.5%, respectively; P<0.05). Regardless of the testing condition, CoP sway area and the perimeter remained similar, while antero-posterior and medio-lateral sway mean speed decreased by ≈8% and ≈12%, respectively (P<0.05). sEMG RMS during the balance tests increased in all muscles in POST (≈7%, P<0.05). All variables recovered in POST30. No changes occurred in CTRL. Passive static stretching did not affect the overall balance control ability. However, greater muscle activation was required to maintain similar CoP sway, thus suggesting a decrease in muscle efficiency.

Long-term effects of asymmetrical posture in boxing assessed by baropodometry.

Asymmetrical posture maintained over long training periods may affect phenotypic plasticity, resulting functional to sporting goal but negative to the locomotor system. Aim of this study was to quantitatively evaluate these long-term effects in competitive boxers. Baropodometric analysis was used to assess 20 competitive boxers and 20 non-sportsmen in upright bipedal posture for 5 s and for 51.2 s with open (OE) and closed (CE) eyes. The boxers' group (BOX) showed a larger total foot load (TFL) (p=0.022) on the right foot and a larger rearfoot load (RfL) (P=0.011) on the left foot compared to non-sport controls (CTR). Moreover, a larger forefoot load (FfL) (P=0.001) on the right foot respect to left one was found in the BOX group, with the inversion of the RfL to FfL ratio (P=0.001) between two feet, while no significant differences were found in the CTR group. These findings, associated to a significantly larger center of foot angle (COF) in the BOX group, may indicate an anticlockwise rotation of the anatomical structures above the ankle joint of the right hemisoma respect to the left one, that appears to be consistent with the orthodox stance. Eventually, the BOX group showed a larger centre-of-pressure sway area (COPsa) in the OE condition than what measured in the CE and a significant difference in Romberg Index (BOX< CTR). The results of this study seem to confirm the theory of neuromuscular plasticity imprinted by the repetitive movements and long-lasting postures. Moreover, competitive boxers show an increase of proprioceptive function and a decrease of visual dependence on the postural control.

Effects of two passive back-support exoskeletons on postural balance during quiet stance and functional limits of stability

While occupational back-support exoskeletons (BSEs) are considered as potential workplace interventions, BSE use may compromise postural control. Thus, we investigated the effects of passive BSEs on postural balance during quiet upright stance and functional limits of stability. Twenty healthy adults completed trials of quiet upright stance with differing levels of difficulty (bipedal and unipedal stance; each with eyes open and closed), and executed maximal voluntary leans. Trials were done while wearing two different BSEs (SuitX™, Laevo™) and in a control (no-BSE) condition. BSE use significantly increased center-of-pressure (COP) median frequency and mean velocity during bipedal stance. In unipedal stance, using the Laevo™ was associated with a significant improvement in postural balance, especially among males, as indicated by smaller COP displacement and sway area, and a longer time to contact the stability boundary. BSE use may affect postural balance, through translation of the human + BSE center-of-mass, restricted motion, and added supportive torques. Furthermore, larger effects of BSEs on postural balance were evident among males. Future work should further investigate the gender-specificity of BSE effects on postural balance and consider the effects of BSEs on dynamic stability.